Installing a deck hatch in my 170 floor

[c master]

My '76 170 is solid, with the exception of a small soft area in the floor between the aft end of the fuel tank "box" and the transom.  This is only due to the PO installing a stainless steel plate/socket there for a bass boat seat.  (I know...I know.  There's no point in discussing that any further.)

In terms of the deck being soft (about a 12" x 12" area) around that installation, nothing has changed since I acquired the boat in 1999.  But I don't like it. 

It's not worth trying to rebuild the entire floor - that would be overkill.  My solution is to cut out that small area and install a flush, white, framed, rectangular deck hatch. The flange under the hatch appears to fit perfectly between the stringers.  When closed, the hatch is waterproof.  The added benefit will be better occasional access to the back of the bilge.  Being in it's own frame, the hatch is very stiff and has a 1.5" lip around it.  Strength-wise it will be fine, especially that close to the stringers.

Question:  Once I cut the hole, I'm hoping to be beyond the soft plywood all the way around, but either way, should I fill the exposed "edge" of the cutout with something like Git Rot and then coat with 5200?  There will also be s/s screws through the hatch lip and I'll bed the whole thing down as well.  So no water will ever get under the edge of the hatch lip. 

[Capt. Bob]

Question:  Once I cut the hole, I'm hoping to be beyond the soft plywood all the way around, but either way, should I fill the exposed "edge" of the cutout with something like Git Rot and then coat with 5200?  There will also be s/s screws through the hatch lip and I'll bed the whole thing down as well.  So no water will ever get under the edge of the hatch lip.

So you cut out the rotted wood and now have fresh (think dry) wood/balsa exposed in the required cutout to mount the hatch. You really want to removed some of this dry wood but leave the fiberglass. That is "indent the core". A handheld router works good for this. Now you can fill the void you created with a compound of epoxy resin and cabosil mixed to the consistency of peanut butter. This gives you a barrier between the nice dry wood and the hatch so when the day comes (and it will come) water that gets past the hatch can't penetrate the epoxy and begin rotting the wood.

If you wish to go further, you would over-drill the mounting holes and refill them with the same epoxy mixture. Once cured, you drill the correct hole size through the epoxy, again insuring the wood core of the deck has a barrier between it and the fastener. Extra work but that's the best way to reduce/eliminate deck rot.

Forget the 5200. For sealing try UV4000.

Good luck.

[c master]

Great information. 
I did the same overdrilling when I reattached the console
years ago. 

The PO also mounted a similar bass seat socket in the middle
of the forward "cooler" hatch.  I guess that's a testament to how well
these boats were built. The hatch is fine.

This boat is going up for sale soon so I'm doing what many of us
do - fix A bunch of little things right before I sell!  Same thing happens with
homes.

(On the upside, I already replaced the belly tank (exact match) and it's sitting on an almost-new aluminum trailer, so those parts are taken care of.)

[minionsram]

Ive been thinking of doing this to my 170 as well. Was wanting to put one in front of the console. Take lots of pictures and let us know how it goes!

[minionsram]

so how did the deck hatch turn out?